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Cell areas in a patch

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Old   April 2, 2014, 08:59
Default Cell areas in a patch
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Euan Foster
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Dear all,

I have a trapezoidal pipe network that I have completed a simulation for. I now need to find the area-weighted average of the wall shear stress of which I need to know the cell area.

Previously all my simulation have been with rectangular cross sections so I have been able to find out the cell area with ease by doing it manually.

I have come across this post about finding the cell areas:

and that subsequently refers you to this post:

They suggest various lines of code to be implemented. But since I am a pretty new user of openFoam and linux in general, I am not too sure of how and where they are implementing this code? Does anyone have any suggestions?

Or an alternative technique?
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Old   April 5, 2014, 09:59
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The answer
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Old   June 21, 2019, 14:51
Default quick regex solution
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TLDR:use this regex code, only tested in openfoam 4!
postProcess -func 'patchIntegrate(name=somePatchName,someFiledName)' | grep -Po "((?<=total area   =).*([0-9])*)"
Full Description:
By using the postProcess function utility we can check the value of a field such as U,p,k,nut, T over a whole patch. To be able to have the integrated value the computer must have an area. Luckily that area gets printed when we perform a funciton such as integrate velocity over a face. So then you can just use regex string to manipulate the return from openfoam. Notes that I am not a regex star, so i did an exact string which requires that there is a line with 'total area' followed by 3 spaces and then an equals sign. If someone else has a better solution then pls supply

  1. change directory to case you want to analyze
  2. punch this in
    (must replace somePatchName, someFieldName

    postProcess -func 'patchIntegrate(name=somePatchName,someFiledName)' | grep -Po "((?<=total area   =).*([0-9])*)"

Here is an applied example in which the "inlet" patch is the one i want to find the area of and I use the U field to get it's area printed. This works because my simulation calculates the velocity. Whether the velocity is a set value or is varied by the solver is irrelevant.

postProcess -func 'patchIntegrate(name=inlet,U)' | grep -Po "((?<=total area   =).*([0-9])*)"
that will print the value to the terminal, in reality this will work with most programming languages bc they all support regex.

While the openfoam naitive compilation is a great solution. Here is a a

Last edited by LeeRuns; June 21, 2019 at 14:54. Reason: cleaning up spacing
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cell, cell area, patch

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